Four bells ring at intervals of 30 minutes, 1 hour, 1 hour 30 min and 1 hour 45 min respectively. All the bells ring simultaneously at 12 noon. They will ring again simultaneously at:
Answer & explanation
Correct answer: option 4
30 min, 60 min, 90 min, 105 min
LCM ⇒ 1260 min
Convert into hour ⇒ \(\frac{1260}{60}\) ⇒ 21 hour
All will ring again simultaneously on next morning at ⇒ 12:00 + 21 hour = 9:00AM